1. Field of the Invention
The present invention relates to an optical transceiver. More specifically, the present invention relates to an optical transceiver which easily houses a plurality of transmission/reception printed boards and transmission/reception optical modules inside a casing whose size is standardized.
2. Description of the Related Art
An optical transceiver including a light emitting module (for transmission) and a light receiving module (for reception) for mutually converting electric signals and optical signal is known.
Regarding the optical transceiver, an optical input/output interface which conducts processor data transmission and reception is known (see Japanese Unexamined Patent Publication Hei 08-043691 (Patent Document 1), for example).
The optical input/output interface disclosed in Patent Document 1 is structured to include an optical fiber module and another neighboring optical fiber module, which makes it possible to improve the data transfer throughput and the packaging density.
Further, also known is an optical transceiver which converts optical signals of a plurality of channels from a first side into electric signals and outputs those to a second side, and converts electric signals of a plurality of channels from the second side to optical signals and outputs those to the first side (see Japanese Patent Application Publication 2010-511907 (Patent Document 2), for example).
The optical input/output interface disclosed in Patent Document 2 is proposed in order to prevent the optical interference and the electric interference between the channels.
Further, an optical transceiver developed to achieve an object different from those of Patent Document 1 and Patent Document 2 described above is known as well.
That is, as a general rule, a transmission optical port and a reception optical port for a signal to be transmitted is of 1 channel in the optical transceiver. However, recently, there has been devised an optical transceiver which includes a plurality of transmission optical ports as well as reception optical ports and connects an optical fiber array due to an increase in the communication bit rate. Accordingly, there have been achieved standardizations of QSFP (Quad Small Form-factor Pluggable; next-generation interface), CXP (120 Gb/s 12× Small Form-factor Pluggable), and the like in Infiniband (next-generation network standards corresponding to servers and inter-storage data transmission).
As described, while the casing size is defined by MSA (Multi Source Agreements; ISO Assessment Organization), with CXP including optical transmission/reception ports of 12 channels, for example, differential electric signals of 24 channels in total for transmission and reception in the small-size casing are to be transmitted inside the casing, and there are a great number of electric connectors for the outside. Thus, regarding a printed board to be a card edge including the connectors, not a single printed board but two printed boards are disposed in parallel. The size and the space to be provided therebetween are also defined by MSA described above.
MSA promotes to define specifications of each of the components in order to satisfy the market demands such as the port density, the power consumption, the performance, and the cost.
Next, the outline of the structure of an optical transceiver 110 including two printed boards 120 as mentioned above will be described by referring to FIG. 7 and FIG. 8.
As shown in FIG. 7 and FIG. 8, the optical transceiver 110 includes: a casing 111; and two printed boards 112, i.e., a transmission printed board 112A and a reception printed board 112B, which are provided inside the casing 111 in parallel with a space therebetween by including electric connector sections 112C, 112C capable of being connected to each other.
At the end of each of the printed boards 112A, 112B on the opposite side of the electric connector sections 112C, 112C, two optical modules 114 which mutually convert the electric signals and the optical signals, i.e., a transmission optical module 114A and a reception optical module 114B, are mounted.
Further, each of the optical modules 114A, 114B is connected to an external output optical connector 117 mounted to the end of the casing on the opposite side of the electric connector sections 112C, 112C of the casing 111 via a pair of optical fiber arrays 116 constituted with a transmission optical fiber array 116A and a reception optical module array 116B. Further, one end of the optical fiber arrays 116 is connected to an optical fiber array-to-optical fiber array connector 119.
FIG. 7 shows a state where a lid (not shown) of the casing 111 is detached, and “upper side” and “lower side” in FIG. 8 show the positional relationship when the optical transceiver 110 is placed in a normal use state.
As shown in FIG. 9, the optical fiber arrays 116 are normally placed in line along the plane direction. Thus, it is difficult to draw them around in the twisting direction, and it is not preferable since the probability of causing deterioration of the property due to damage or nonuniformity in the stress of each fiber is high.
Thus, to mount the optical modules 114A and 114B by tilting them or by changing the facing directions is difficult, since the layout of the optical connector 117 is defined.
Therefore, as shown in FIG. 7, FIG. 9, and FIG. 10, it is necessary to place the optical modules 114A and 1148 to be in parallel to the layout of each of the ports 120 of the optical connector 117. In that case, it is the simplest way to employ a structure in which those are directly mounted on the top faces of each of the printed boards 112A and 112B.
In the meantime, regarding the optical transmission/reception ports, MSA defines the structure of 12×2 as the layout of the ports of 24 channels in total for transmission and reception. However, as shown in details in FIG. 8, the space between the two optical modules, that is, the space (distance D) from the transmission optical module 114A and the reception optical module 114B to the optical output port and the space between the two printed boards 112 located vertically (see FIG. 8) are largely different from each other. Thus, it is necessary to adjust the positions thereof.
However, even though the optical input/output interface disclosed in Patent Document 1 is formed in the structure that can improve the data transfer throughput and the packaging density, the structure corresponding to MSA is not mentioned therein.
Also, even though the optical transceiver disclosed in Patent Document 2 is formed in the structure which prevents the optical interference and the electric interference generated between the neighboring channels, the structure corresponding especially to the height defined by MSA is not mentioned in the disclosure regarding the optical transceiver.
Furthermore, there are following issues with the optical transceiver 110 shown in FIG. 7 and FIG. 8.
That is, in the optical transceiver 110, the transmission and reception optical modules 114A and 114B are mounted on each of the printed boards 112A and 112B. However, the height A inside the casing 111 and the distance B between the two printed boards 112A and 112B are defined by MSA, so that it is difficult to mount the transmission optical module 114A and the reception optical module 114B directly on the printed boards 112A and 112B depending on the height C of each of the optical modules 114A and 114B because of the restriction of the size.
Further, regarding the optical fiber arrays 116 to be the paths from each of the optical modules 114A and 114B to the optical connector 117 of the casing 111, it is necessary to have the distance D sufficient for the distance B between the boards because of the restriction of the minimum radius curvature r. As a result, there faces an issue in terms of reducing the size of the optical transceiver 110.
Further, the two printed boards 112A and 112B directly receive the oscillation from the outside and the impact generated by attaching detaching the external connector of the optical transceiver 110, which may result in damaging the optical fiber arrays 116 due to the oscillation and impact and may result in the optical axis shift generated in the junction parts between each of the optical modules 114A, 1148 and the optical fiber arrays 116.
In order to overcome each of the aforementioned issues, it is therefore an exemplary object of the present invention to provide an optical transceiver with which at least a pair of printed boards disposed in parallel having respective electric connector sections and at least a pair of transmission and reception optical modules can be easily housed inside a casing whose size is standardized, and the size thereof can be reduced.